516 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



tt id metabolism. In a starving dog, which feeds on its own proteid, it was 

 found that a ratio existed between nitrogen and phosphoric acid in the urine as 

 0.4:1, which approximates that in muscle, i.e. 7.6:1. On feeding meat till 

 nitrogenous equilibrium was established, the ratio became 8.1 : l. 1 On addi- 

 tion of proteid to the body, a proportionate amount of phosphoric acid is re- 

 tained for the new protoplasm, while on destruction of proteid the phosphoric 

 acid corresponding to it is eliminated. In diabetes where the proteid metab- 

 olism i> far above the normal, the phosphorus excretion remains propor- 

 tional to the proteid destroyed. 2 The larger excretion of phosphoric acid 

 during hunger shown in the ratio above, has been ascribed to the decomposi- 

 tion of the bones. 3 Thus Munk found on Cetti, who lived many days without 

 food, a ratio as low as 4.5:1. In starvation the brain and nerves do not 

 decrease in weight, so the protagon can hardly yield any great amount of phos- 

 phoric acid (Voit). Casein and other nucleo-albumins, when fed, are oxidized 

 and furnish phosphoric acid for the urine. 



Carbon, C = 12. 



This element is found combined in every organism, and in many decom- 

 position-products of organized matter. Elementary carbon occurs as lamp- 

 black, diamond, and graphite, the two latter having their origin from the action 

 of high heat on coal. Carbon occurs combined in coal, petroleum, and natural 

 gas, which are all products of the decomposition of wood out of contact with the 

 air. Further it is found in vast masses, principally consisting of calcium car- 

 bonate, having their origin from sea-shells. The maintenance of life depends, as 

 will be shown, on the small percentage of carbon dioxide which is contained in the 

 atmosphere. Lavoisier believed that compounds of carbon were all products 

 of life, formed under the influence of a '" vital force," which was a property 

 of the cell. It is now known that almost every constituent of the cell may be 

 prepared from its elements in the laboratory without the aid of any "vital 

 force" whatever. Notwithstanding its loss of strict scientific significance, the 

 old term "organic" for a carbon compound is still in vogue, and conveniently 

 describes a large number of bodies which are treated under the head of "or- 

 ganic chemistry," while the term "inorganic" is applied to the rest of the 

 chemical world. 



Elementary Carbon. — This burns only at a high heat. It is unaffected 

 by the intestinal tract. This is shown by the fact that diamonds have been 

 stolen by -wallowing them, and that finely divided particles of lampblack pass 

 unchanged and unabsorbed to the feces, coloring them black (proof that the 

 intestinal canal does not absorb solid particles). If lampblack be eaten with a 

 meal its appearance in the feces may be used as a demarcation line between the 



1 E. Bischoff: Zeilschrift jr,,- Bidogie, 1867, Bd. 3, S. 309. 



2 Colaasanti e Bounani: Boll. <l. II. A'<-'t</. med. ili Roma, 1896-1897; Reilly, Nolan, and 

 Lusk : American Journal of Physiology, 1898, vol. i. p. 395. 



3 See Voit : Hermann's Handbueh, L8S1, vi. 1, s. 79. 



